Ascorbic acid derivatives and skin-whitening cosmetics

ABSTRACT

It is an object to provide an L-ascorbic acid derivative which can keep the L-ascorbic acid stable to heat and light and thus has a long shelf life, which is high in permeability into the skin, which can be quickly hydrolyzed by phosphatase, an enzyme that is ubiquitous in vivo, and which exhibits physiological activities that are inherent to L-ascorbic acid and beneficial to health, a method for producing such an L-ascorbic acid derivative, and a skin-whitening cosmetic material. 
     There is provided an ascorbic acid derivative comprising an L-ascorbic acid-2-phosphate ester or a salt thereof wherein the phosphate ester has a branched alkyl group, the L-ascorbic acid-2-phosphate ester being of formula [13]. The ascorbic acid derivative is produced by a method comprising reacting a branched alkanol with phosphorus oxychloride to synthesize monoalkyldichlorophosphate or dialkylmonochlorophosphate, reacting the thus obtained substance with 5,6-O-isopropylidene-L-ascorbic acid obtained by reacting L-ascorbic acid with acetone, and subjecting the thus obtained substance to acid hydrolysis. There is also provided a cosmetic material containing such an ascorbic acid derivative by 0.05 to 80 percent by weight. 
                         
(wherein each of R 1  and R 2  is a hydrogen (H) atom or an alkyl group having branches and including 3 to 30 carbon atoms, but not both of R 1  and R 2  are hydrogen (H) atoms).

TECHNICAL FIELD

This invention relates to ascorbic acid derivatives that are useful ascosmetics and quasi drugs used for whitening human skin, a method formanufacturing the same, and skin-whitening cosmetics.

BACKGROUND ART

It is generally known that L-ascorbic acid (vitamin C) has, besides thefunction of inhibiting lipid peroxides, the functions of promoting theproduction of collagen and strengthening the immune system, thefunctions of inhibiting the synthesis of melanin under the skin andreducing and fading any black melanin that has been synthesized. Thus,L-ascorbic acid is a well-known component of skin-whitening cosmeticsthat can inhibit the synthesis and/or reduce synthesized melanin,thereby inhibiting “spots” and “freckles”.

L-ascorbic acid is extremely unstable to heat or oxidation and tend tobecome inert or decompose when heated or oxidized. This may make itdifficult for L-ascorbic acid to fully exhibit its expectedphysiological function.

In order to prevent L-ascorbic acid from becoming unstable, there areknown a derivative in which the diol portion of L-ascorbic acid, whichis prone to oxidation, is subjected to phosphate esterification (Patentpublication 1), and a derivative in which the diol portion is subjectedto glycosidation (Patent publication 2).

But because these L-ascorbic acid derivatives are high inhydrophilicity, they are low in permeability into the skin.

In order to improve permeability of L-ascorbic acid into the skin, thereare known an L-ascorbic acid derivative in which position 6 ofL-ascorbic acid is acylated (Patent document 3), and a derivative inwhich position 4 of L-ascorbic acid is acylated (Patent document 4).

An L-ascorbic acid derivative is also known which shows both superiorstability and permeability into the skin by acylating position 6 ofL-ascorbic acid and further subjecting position 2 to phosphateesterification (Patent publication 5).

-   Patent document 1: JP patent publication 52-18191B-   Patent document 2: JP patent publication 03-139288A-   Patent document 3: JP patent publication 59-170085A-   Patent document 4: JP patent publication 45-23634B-   Patent document 5: JP patent publication 10-298174A

DISCLOSURE OF THE INVENTION

Problems to which the Invention Seeks a Solution

However, the derivative in which position 6 of L-ascorbic acid isacyl-esterified with fatty acid is not sufficient in chronologicalstability to heat and light during storage. The derivative in whichposition 2 is acyl-esterified with fatty acid cannot be quickly orsufficiently converted to L-ascorbic acid in the skin because nosufficient amount of esterase or lipase is present in the skin.

The derivative in which position 6 of L-ascorbic acid is acyl-esterifiedand position 2 is subjected to phosphate esterification cannot also besufficiently converted to L-ascorbic acid in the skin because nosufficient amount of esterase or lipase is present in the skin.

Therefore, it is an object of the present invention to provide a novelL-ascorbic acid derivative which can keep the L-ascorbic acid stable toheat and light and thus has a long shelf life, which is high inpermeability into the skin, which can be quickly hydrolyzed byphosphatase, a substance that is ubiquitous in vivo, and which exhibitsphysiological activities that are inherent to L-ascorbic acid andbeneficial to health, and a method for producing such an L-ascorbic acidderivative.

Another object of the present invention is to provide a skin-whiteningcosmetic material which can keep the L-ascorbic acid stable to heat andlight and thus has a long shelf life, which is high in permeability intothe skin, which can be quickly decomposed by enzymes that are ubiquitousin vivo, and which exhibits physiological activities that are inherentto L-ascorbic acid and beneficial in whitening the skin.

Means to Solve the Problems

According to the present invention, there is provided an ascorbic acidderivative comprising an L-ascorbic acid-2-phosphate ester or a saltthereof wherein the phosphate ester has a branched alkyl group, theL-ascorbic acid-2-phosphate ester being of formula [5]

(wherein each of R¹ and R² is a hydrogen (H) atom or an alkyl grouphaving branches and including 3 to 30 carbon atoms, but not both of R¹and R² are hydrogen (H) atoms).

The phosphate ester, which is located at position 2 of the ascorbic acidderivative and has the branched alkyl group, provides suitable oilsolubility to the derivative, thereby allowing the derivative to beeasily absorbed into cells.

Except the phosphate alkyl ester portion, the ascorbic acid derivativeaccording to the present invention is not modified at all, so that onceit permeates into the skin, even without esterase or lipase, thederivative is hydrolyzed into L-ascorbic acid (vitamin C),phospholipids, etc. by enzymes such as phosphatase, which is ubiquitousin vivo. The derivative has thus a beneficial influence on the body.

The branched alkyl group is typically 2-heptylundecyl group,2-octyldecyl group, 2-octyldodecyl group, 2-hexyldecyl group,2-hexyl-dodecyl group, 2-isoheptylisoundecyl group, 16-methylheptadecylgroup or 2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl group.

If the derivative is a salt, it is preferably a sodium salt, potassiumsalt, magnesium salt or calcium salt of L-ascorbic acid-2-phosphateester.

The ascorbic acid derivative may be produced by a process comprisingreacting a branched alkanol of formula [6] with phosphorus oxychlorideto synthesize monoalkyldichlorophosphate of formula [7] ordialkylmonochlorophosphate of formula [8], reacting the thus obtainedsubstance with 5,6-O-isopropylidene-L-ascorbic acid obtained by reactingL-ascorbic acid with acetone, and subjecting the thus obtained substanceto acid hydrolysis.R—OH  [6](wherein R is an alkyl group having branches and including 3 to 30carbon atoms)

(wherein R is an alkyl group having branches and including 3 to 30carbon atoms)

(wherein each of R¹ and R² is a hydrogen (H) atom or an alkyl grouphaving branches and including 3 to 30 carbon atoms, but not both of R¹and R² are hydrogen (H) atoms).

In order to solve the problems of conventional skin-whitening cosmetics,there is provided a skin-whitening cosmetic material containing anascorbic acid derivative comprising an L-ascorbic acid-2-phosphate esteror a salt thereof wherein the phosphate ester has a branched alkylgroup, the L-ascorbic acid-2-phosphate ester being of formula [5].

The phosphate ester, which is located at position 2 of the ascorbic acidderivative and has the branched alkyl group, provides suitable oilsolubility to the derivative, thereby allowing the derivative to beeasily absorbed into cells.

Except the phosphate alkyl ester portion, the ascorbic acid derivativeaccording to the present invention is not modified at all, so that onceit permeates into the skin, even without esterase or lipase, thederivative is hydrolyzed into L-ascorbic acid (vitamin C),phospholipids, etc. by enzymes such as phosphatase, which is ubiquitousin vivo. The derivative can thus whiten the skin.

In order for the skin-whitening cosmetic material according to thepresent invention to fully exhibit its skin-whitening effect, thecontent of the L-ascorbic acid-2-phosphate ester or its salt that arecontained in the cosmetic material is preferably 0.05 to 80 percent byweight.

The skin-whitening cosmetic material has preferably a pH value of 4.0 to9.0 in order to stabilize the ascorbic acid derivative, thereby allowingthe ascorbic acid derivative to fully exhibit the expected effect.

ADVANTAGES OF THE INVENTION

Since the L-ascorbic acid according to the present invention is anL-ascorbic acid-2-phosphate ester or its salt of which the phosphateester has a branched alkyl group, the L-ascorbic acid, which isotherwise unstable to heat and oxidation, stabilizes. Thus, it ispossible to inhibit decomposition of the L-ascorbic acid during storagebefore use. During use, the ascorbic acid derivative according to thepresent invention is quickly decomposed into L-ascorbic acid,phospholipids, etc. by phosphatase, which is ubiquitous in vivo. Thus,the ascorbic acid derivative according to the present invention exhibitsphysiological activities that are inherent to L-ascorbic acid andbeneficial to health.

The skin-whitening cosmetic material according to the present inventioncontains as its active ingredient L-ascorbic acid comprising anL-ascorbic acid-2-phosphate ester of which the phosphate ester has abranched alkyl group or its salt. Thus, the L-ascorbic acid becomesstable to heat and oxidation, so that the L-ascorbic acid is less likelyto decomposed during storage before use. During use, the cosmeticmaterial according to the present invention is quickly decomposed intoL-ascorbic acid, phospholipids, etc. by enzymes that are ubiquitous inthe skin such as phosphatase, so that the cosmetic material according tothe invention exhibits physiological activities that are inherent toL-ascorbic acid and beneficial in whitening the skin. For example, thecosmetic material according to the present invention prevents “spots”and “freckles”. By adjusting the pH value within the predeterminedrange, the ascorbic acid derivative will exhibits the expected functionmore effectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the process for producing the ascorbic acid derivative ofExample 1, using reaction formulas; and

FIG. 2 shows the process for producing the ascorbic acid derivative ofExample 6, using reaction formulas.

BEST MODE FOR EMBODYING THE INVENTION

The L-ascorbic acid-2-phosphate ester of formula [5], i.e. 2-(branchedalkyl)-L-ascorbyl phosphate is produced as follows:

First, using a nonpolar solvent selected from toluene, chlorobenzene,dichlorobenzene, etc., a branched alkanol of formula [6] is reacted withphosphorus oxychloride at −20 to 20 degrees Celsius in the presence of abase selected from trimethylamine, triethylamine, N,N-dimethylaniline,etc. to produce a monoalkyldichlorophosphate of formula [7] or adialkyl-monochlorophosphate of formula [8]. The thus produced substancemay be supplied to the next step after being isolated by distillation orin the form of a solution in the nonpolar solvent.

In the next step, the thus produced monoalkyldichlorophosphate ordialkylmonochlorophosphate is reacted with5,6-O-isopropylidene-L-ascorbic acid obtained by reacting L-ascorbicacid with acetone, and the reaction product is hydrolyzed by acid andpurified by a conventional method to produce the L-ascorbicacid-2-phosphate ester of formula [5].

Branched alkanols of formula [6] include 2-methyldecanol,2-ethyldecanol, 2-propyldecanol, 2-butyldecanol, 2-pentyldecanol,2-hexyldecanol, 2-heptyldecanol, 2-octyldecanol, 2-nonyldecanol,2-methyl-undecanol, 2-ethylundecanol, 2-propylundecanol,2-butylundecanol, 2-pentylundecanol, 2-hexylundecanol,2-heptylundecanol, 2-octylundecanol, 2-nonylundecanol, 2-decylundecanol,2-methyldodecanol, 2-ethyldodecanol, 2-propyldodecanol,2-butyldodecanol, 2-pentyldodecanol, 2-hexyldodecanol,2-heptyldodecanol, 2-octyldodecanol, 2-nonyldodecanol, 2-decyldodecanol,2-undecyldodecanol and 2-isoheptylisoundecanol, and also includealkanols having branches at positions other than position 2, such as16-methylheptadecanol and2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octanol.

5,6-O-isopropylidene-L-ascorbic acid is produced by reacting L-ascorbicacid with acetone in the presence of a dehydrating agent such as acetylchloride or fuming sulfuric acid at −30 to 20 degrees Celsius, andisolating it by e.g. filtering.

In the next step, using a nonpolar solvent selected from toluene,chlorobenzene, dichlorobenzene, etc., the thus obtained5,6-O-isopropylidene-L-ascorbic acid is reacted withmonoalkyldichlorophosphate of formula [7] or dialkylmonochlorophosphateof formula [8] at −20 to 20 degrees Celsius in the presence of a baseselected from trimethylamine, triethylamine, N,N-dimethylaniline, etc.,and the thus obtained substance is hydrolyzed by an acid selected fromhydrochloric acid, sulfuric acid, acetic acid, etc. at −10 to 50 degreesCelsius.

During this step, in order to remove any remaining base, the substanceis washed with an acid such as hydrochloric acid, sulfuric acid oracetic acid or an aqueous solution of an inorganic salt such as sodiumchloride, potassium chloride, ammonium chloride, sodium carbonate,potassium carbonate or sodium hydrogen carbonate, and the nonpolarsolvent is removed by evaporation. If higher quality is desired,2-(branched alkyl)-L-ascorbyl phosphate of formula [5] is isolated bycolumn chromatography. Alternatively, it may be supplied to the nextstep in the form of an ethanol or glycerol solution. Thus, the ascorbicacid derivative according to the present invention can be isolated andpurified by any ordinary method.

Specific compounds of the ascorbic acid derivative of formula [5]according to the present invention include 2-(2-methyldecyl)-L-ascorbylphosphate, 2-(2-ethyldecyl)-L-ascorbyl phosphate,2-(2-propyldecyl)-L-ascorbyl phosphate, 2-(2-butyldecyl)-L-ascorbylphosphate, 2-(2-pentyldecyl)-L-ascorbyl phosphate,2-(2-hexyldecyl)-L-ascorbyl phosphate, 2-(2-heptyldecyl)-L-ascorbylphosphate, 2-(2-octyldecyl)-L-ascorbyl phosphate,2-(2-nonyldecyl)-L-ascorbyl phosphate, 2-(2-methylundecyl)-L-ascorbylphosphate, 2-(2-ethylundecyl)-L-ascorbyl phosphate,2-(2-propylundecyl)-L-ascorbyl phosphate, 2-(2-butylundecyl) -L-ascorbylphosphate, 2-(2-pentylundecyl)-L-ascorbyl phosphate,2-(2-hexylundecyl)-L-ascorbyl phosphate, 2-(2-heptylundecyl)-L-ascorbylphosphate, 2-(2-octylundecyl)-L-ascorbyl phosphate,2-(2-nonylundecyl)-L-ascorbyl phosphate, 2-(2-decylundecyl)-L-ascorbylphosphate, 2-(2-methyldodecyl)-L-ascorbyl phosphate,2-(2-ethyldodecyl)-L-ascorbyl phosphate, 2-(2-propyldodecyl)-L-ascorbylphosphate, 2-(2-butyldodecyl)-L-ascorbyl phosphate,2-(2-pentyldodecyl)-L-ascorbyl phosphate, 2-(2-hexyldodecyl)-L-ascorbylphosphate, 2-(2-heptyldodecyl)-L-ascorbyl phosphate,2-(2-octyldodecyl)-L-ascorbyl phosphate, 2-(2-nonyldodecyl)-L-ascorbylphosphate, 2-(2-decyldodecyl)-L-ascorbyl phosphate,2-(2-undecyldodecyl)-L-ascorbyl phosphate,2-(2-isoheptyl-isoundecyl)-L-ascorbyl phosphate,2-(16-methylheptadecyl)-L-ascorbyl phosphate,2-bis(2-methyldecyl)-L-ascorbyl phosphate,2-bis(2-ethyldecyl)-L-ascorbyl phosphate,2-bis(2-propyldecyl)-L-ascorbyl phosphate,2-bis(2-butyldecyl)-L-ascorbyl phosphate,2-bis(2-pentyldecyl)-L-ascorbyl phosphate,2-bis(2-hexyldecyl)-L-ascorbyl phosphate,2-bis(2-heptyldecyl)-L-ascorbyl phosphate,2-bis(2-octyldecyl)-L-ascorbyl phosphate, 2-bis(2-nonyldecyl)-L-ascorbylphosphate, 2-bis(2-methylundecyl)-L-ascorbyl phosphate,2-bis(2-ethylundecyl)-L-ascorbyl phosphate,2-bis(2-propylundecyl)-L-ascorbyl phosphate,2-bis(2-butylundecyl)-L-ascorbyl phosphate,2-bis(2-pentylundecyl)-L-ascorbyl phosphate,2-bis(2-hexylundecyl)-L-ascorbyl phosphate,2-bis(2-heptylundecyl)-L-ascorbyl phosphate,2-bis(2-octylundecyl)-L-ascorbyl phosphate,2-bis(2-nonylundecyl)-L-ascorbyl phosphate,2-bis(2-decylundecyl)-L-ascorbyl phosphate,2-bis(2-methyldodecyl)-L-ascorbyl phosphate,2-bis(2-ethyldodecyl)-L-ascorbyl phosphate,2-bis(2-propyldodecyl)-L-ascorbyl phosphate,2-bis(2-butyldodecyl)-L-ascorbyl phosphate,2-bis(2-pentyldodecyl)-L-ascorbyl phosphate,2-bis(2-hexyldodecyl)-L-ascorbyl phosphate,2-bis(2-heptyldodecyl)-L-ascorbyl phosphate,2-bis(2-octyldodecyl)-L-ascorbyl phosphate,2-bis(2-nonyldodecyl)-L-ascorbyl phosphate,2-bis(2-decyldodecyl)-L-ascorbyl phosphate,2-bis(2-undecyldodecyl)-L-ascorbyl phosphate,2-bis(2-isoheptylisoundecyl)-L-ascorbyl phosphate,2-bis(16-methylheptadecyl)-L-ascorbyl phosphate, and2-bis[2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]-L-ascorbylphosphate. The abovementioned compounds all include alkyl groupsbranched at position 2. But needless to say, the ascorbic acidderivative according to the present invention may be one including analkyl group branched at a position other than position 2, such as2-[2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]-L-ascorbylphosphate.

The ascorbic acid derivative according to the present invention may bereplaced with one of salts thereof including alkali metal salts such assodium salts and potassium salts, alkali earth metal salts such ascalcium salts and magnesium salts, basic amino acids such as arginine,and organic amines such as triethanolamine.

In order for the skin-whitening cosmetic material according to thepresent invention to fully reveal its skin-whitening function, itpreferably contains such L-ascorbic acid-2-phosphate ester or its saltin an amount of 0.05 to 80 percent by weight. If its content is lessthan 0.05 percent by weight, the cosmetic material will not reveal itsskin-whitening function at all or reliably. If its content exceeds 80percent by weight, the cosmetic material may not give good feelings tothe user when applied to the skin. Thus, more preferably, the cosmeticmaterial contains the above substance in an amount of 2 to 50 percent byweight.

The pH value of the skin-whitening cosmetic material according to thepresent invention is not particularly limited. But preferably, thecosmetic material according to the invention has a pH value of 4.0 to9.0 to improve stability during storage. Outside this range, the estertends to hydrolyze, thus destabilizing the cosmetic material.

Besides the abovementioned essential components, the skin-whiteningcosmetic material according to the present invention may containcomponents used in ordinary cosmetics, drugs and quasi drugs, such asoil components, emulsifiers, humectants, thickeners, active drugcomponents, preservatives, pigments, powders, pH adjusters, UVabsorbers, antioxidants and perfumes.

Specific oil components include liquid paraffin, Vaseline,microcrystalline wax, squalane, jojoba oil, beeswax, carnauba wax,lanoline, olive oil, coconut oil, higher alcohols, fatty acids, estersof higher alcohols and fatty acids and silicone oil. Specificemulsifiers include nonionic surfactants such as polyoxyethylene alkylether, polyoxyethylene fatty ester, polyoxyethylene sorbitan fattyester, sorbitan fatty ester, glycerin fatty ester, polyglycerin fattyester and polyoxyethylene hydrogenated castor oil, anionic surfactantssuch as sodium stearoyl lactate, amphoteric surfactants such as soyphospholipid, and cationic surfactants such as alkyltrimethyl ammoniumchloride. Specific humectants include glycerin, sorbitol, xylitol,maltitol, propylene glycol, polyethylene glycol, 1,3-butylene glycol,and 1,2-pentanediol. Specific thickeners include carboxyvinyl polymer,xanthan gum, methylcellulose, polyvinyl pyrolidone, gelatin and clayminerals such as bentonite. Specific active drug components includevitamins, their derivatives, allantoin, glycyrrhetinic acid and itsderivatives, and animal and vegetable extracts.

The skin-whitening cosmetic material according to the present inventionis not specifically limited, provided it contains the above-describedascorbic acid derivative as a skin-whitening active ingredient, and canbe produced by a known method employed to produce ordinary cosmeticmaterials. The skin-whitening cosmetic material can be used not only asgeneral-purpose skin cosmetics but as quasi drugs and external drugs,and may be provided in various forms, e.g. in the form of cream,emulsion, liquid, gel, ointment, packs, sticks or powder.

EXAMPLE 1

[Production Example 1 of Ascorbic Acid Derivative]

As will be apparent from the production steps shown by reaction formulasin FIG. 1, 2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octanol, whichis a branched alkanol, was reacted with phosphorus oxychloride tosynthesize [2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]dichloro-phosphate, which is a monoalkyl dichlorophosphate. The thussynthesized substance was reacted with 5,6-O-isopropylidene-L-ascorbicacid obtained by reacting L-ascorbic acid with acetone, and the thusproduced isostearyl-2-O-isopropylidene ascorbyl phosphate was hydrolyzedwith hydrochloric acid, washed, isolated and purified to produce2-(2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl)-L-ascorbylphosphate. (In FIG. 1, the assigned numbers of peaks at ¹³C-NMR, whichis described later, are indicated.) Now the individual synthesis stepsare described in detail.

(1) Synthesis of 5,6-O-isopropylidene-L-ascorbic acid

With nitrogen substitution, 557.8 grams (9.6 moles) of acetone wascooled to −5 degrees C., 54.3 grams (0.2 moles) of 28% fuming sulfuricacid was dripped, and 176.1 grams (1.0 mole) of L-ascorbic acid wasadded. The mixture was then reacted at the temperature of the previousstep for 17 hours, filtered and washed with cold acetone to obtain 249.5grams of 5,6-O-isopropylidene-L-ascorbic acid (86.7% in purity) in theform of a wet cake.

(2) Synthesis of [2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]dichlorophosphate

With nitrogen substitution, 540 ml of toluene and 138.0 grams (0.9moles) of phosphorus oxychloride were added and cooled to −10 degrees C.To this mixture, a solution of 243.5 grams (0.9 moles; 1.0 in molarratio) of 2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octanol and 91.1grams (0.9 moles) of triethylamine was dripped, and the mixture wasreacted for 12 hours at 0 degrees C. The mixture was then heated to 25degrees C., and a triethylamine hydrochloride was removed by filteringto obtain 1003.9 grams of a toluene solution of[2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]dichlorophosphate(34.7% in concentration).

(3) Synthesis of2-[2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]-L-ascorbylphosphate

With nitrogen substitution, 249.5 grams (1.0 mole) of5,6-O-isopropylidene-L-ascorbic acid was added to 2000 ml of toluene,202.4 grams of triethylamine was dripped at room temperature, and themixture was stirred for one hour. Then, the mixture was cooled to −10degrees C., and 1003.9 grams (0.9 moles) of a toluene solution of[2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]dichlorophosphatewas dripped for one hour, and the mixture was stirred at the temperaturein the previous step for 14 hours. To the thus obtained reaction mass,12312 grams of an aqueous solution of 6.7% hydrochloric acid was added,the mixture was hydrolyzed at 35 degrees C. for four hours, and thetoluene layer was washed twice with 1000 grams of an aqueous solution of10% hydrochloric acid and 7.1% sodium chloride, and further washed oncewith an aqueous solution of 20% sodium chloride. The toluene layer wasthen subjected to column chromatography, and a separated fractionthereof was subjected to vacuum concentration (35 degrees C.; 2 Torr) toremove toluene by distillation to obtain 338.9 grams of2-[2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]-L-ascorbylphosphate (94.6% in purity). The yield was 66.6% (based on L-ascorbicacid).

The molecular structure of the thus obtained2-[2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]-L-ascorbylphosphate was identified by infrared absorption spectrum (IR) andnuclear magnetic resonance spectrum (¹H-NMR, ¹³C-NMR). The results(groups or carbon atoms corresponding to the peak positions) are shownin Tables 1 to 3. It was confirmed that the thus obtained compound wasan ascorbic acid derivative having the desired molecular structure, i.e.2-[2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]-L-ascorbylphosphate.

TABLE 1 IR KBr (cm⁻¹) 3370 (OH) 2954 (CH₂) 2904 (CH) 2867 (CH₂) 2715(P—OH) 1765 (C═O) 1673 (C═C) 1473 (CH₃) 1216 (P═O) 1043 (P—O—C)

TABLE 2 ¹H-NMR δ (ppm) from TMS in CDCl₃ 1.02 (CH₃-15, 24, t, 6H) 1.30(CH₂-9~16, 18~23, bs, 28H) 1.54 (CH-8, bs, 1H) 1.71 (6-OH, bs, 1H) 1.80(5-OH, bs, 1H) 3.47 (CH₂-7, m, 2H) 3.61 (CH₂-6, m, 2H) 3.97 (CH-5, m,1H) 4.76 (CH-4, m, 1H)

TABLE 3 ¹³C-NMR δ (ppm) from TMS in CDCl₃ 169.8174 (C-1) 159.2013 (C-3)114.209 (C-2) 77.515 (C-4) 69.4838 (C-6) 69.4265 (C-5) 63.0931 (C-7)38.0741 (C-8) 31.2065 (C-18) 31.0443 (C-20) 30.0714 (C-22) 30.0333(C-11) 29.9474 (C-15) 29.9093 (C-9) 29.8139 (C-13) 29.7376 (C-12)29.6803 (C-21) 29.5563 (C-14) 29.0127 (C-19) 28.8314 (C-10) 22.6029(C-16) 22.4789 (C-23) 18.7399 (C-17) 18.6159 (C-24)

EXAMPLE 2

[Production Example 2 of Ascorbic Acid Derivative]

Except that 2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octanol asused in Example 1 was used in the molar ratio of 2.0 based on phosphorusoxychloride, a compound was produced in exactly the same manner as inExample 1. The compound obtained was identified by infrared absorptionspectrum (IR) and nuclear magnetic resonance spectrum (¹H-NMR, ¹³C-NMR).The results (groups or carbon atoms corresponding to the peak positions)are shown in Tables 4 to 6.

It was confirmed that the thus obtained compound was an ascorbic acidderivative having the desired molecular structure, i.e.2-bis[2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]-L-ascorbylphosphate (91.1% in purity). The yield was 20.1% (based on L-ascorbicacid).

The molecular structure of the thus obtained compound is shown byformula [9], which includes the assigned numbers of peaks at ¹³C-NMR.

TABLE 4 [9]

KBr IR (cm⁻¹) 3394 (OH) 1731 (C═C) 2955 (CH₂) 1469 (CH₃) 2905 (CH) 1204(P═O) 1776 (C═O) 1034 (P—O—C)

TABLE 5 ¹H-NMR δ (ppm) from TMS in CD₃OD 0.90~0.95 (CH₃-17, 24, 34, 41,CH₂-9~16, 18~23, 28~35, 37~42, bs, 40H) 3.67 (CH₂-7, m, 2H) 3.92 (CH-5,m, 1H) 4.15 (CH₂-6, m, 2H)

TABLE 6 ¹³C-NMR δ (ppm) from TMS in CD₃OD 169.8174 (C-1) 159.2013 (C-3)114.209 (C-2) 77.515 (C-4) 69.4838 (C-7) 69.4265 (C-5) 63.0931 (C-6)53.4022 (C-8) 48.5567 (C-9) 48.2992 (C-11) 38.0741 (C-13) 37.8547 (C-18)37.7402 (C-22) 37.4732 (C-16) 37.4255 (C-20) 29.0127 (C-19) 28.8314(C-12) 28.6502 (C-21) 28.5548 (C-10) 26.1321 (C-17) 25.9795 (C-14)25.9127 (C-23) 18.7399 (C-15) 18.6159 (C-24)

EXAMPLE 3

[Production Example 3 of Ascorbic Acid Derivative]

Except that instead of2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octanol as used in Example1, 2-hexyldecanol was used, a compound was produced in exactly the samemanner as in Example 1. The compound obtained was identified by infraredabsorption spectrum (IR) and nuclear magnetic resonance spectrum(¹H-NMR, ¹³C-NMR). The results (groups or carbon atoms corresponding tothe peak positions) are shown in Tables 7 to 9.

It was confirmed that the thus obtained compound was an ascorbic acidderivative having the desired molecular structure, i.e.2-(2-hexyldecyl)-L-ascorbyl phosphate (69.7% in purity). The yield was63% (based on L-ascorbic acid).

The molecular structure of the thus obtained compound is shown byformula [10], which includes the assigned numbers of peaks at ¹³C-NMR.

TABLE 7 [10]

KBr IR (cm⁻¹) 3352 (OH) 1677 (C═C) 2956 (CH₂) 1467 (CH₃) 2926 (CH) 1219(P═O) 2856 (CH₂) 1040 (P—O—C) 1764 (C═O)

TABLE 8 ¹H-NMR δ (ppm) from TMS in CD₃OD 0.89 (CH₃-15, 23, t, 6H)1.10~1.33 (CH₂-9~14, 16~23, bs, 26H) 1.60 (CH-8, bs, 1H) 3.43 (CH₂-7, d,J=5.2 Hz, 2H) 3.67 (CH₂-6, m, 2H) 3.93 (CH-5, m, 1H) 4.90 (CH-4, m, 1H)

TABLE 9 ¹³C-NMR δ (ppm) from TMS in CD₃OD 161.4093 (C-1) 161.3807 (C-3)— (C-2) 76.9187 (C-4) 71.6154 (C-6) 70.4708 (C-5) 63.2884 (C-7) 39.9386(C-8) 33.0614 (C-13) 32.9756 (C-21) 31.7928 (C-9) 31.0393 (C-16) 30.7341(C-10) 30.7055 (C-11) 30.6578 (C-19) 30.4384 (C-12) 27.9203 (C-20)27.7295 (C-17) 27.7104 (C-18) 23.7234 (C-14) 23.7234 (C-22) 14.4331(C-15) 14.4331 (C-23)

EXAMPLE 4

[Production Example 4 of Ascorbic Acid Derivative]

Except that instead of2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octanol as used in Example1, 2-octyldodecanol was used, a compound was produced in exactly thesame manner as in Example 1. The compound obtained was identified byinfrared absorption spectrum (IR) and nuclear magnetic resonancespectrum (¹H-NMR, ¹³C-NMR). The results (groups or carbon atomscorresponding to the peak positions) are shown in Tables 10 to 12.

It was confirmed that the thus obtained compound was an ascorbic acidderivative having the desired molecular structure, i.e.2-(2-octyldodecyl)-L-ascorbyl phosphate (87.0% in purity). The yield was45.4% (based on L-ascorbic acid).

The molecular structure of the thus obtained compound is shown byformula [11], which includes the assigned numbers of peaks at ¹³C-NMR.

TABLE 10 [11]

KBr IR (cm⁻¹) 3320 (OH) 1662 (C═C) 2924 (CH) 1467 (CH₃) 2854 (CH₂) 1220(P═O) 1759 (C═O) 1043 (P—O—C)

TABLE 11 ¹H-NMR δ (ppm) from TMS in CD₃OD 0.89 (CH₃-18, 26, t, J=6.9,6H) 1.28 (CH₂-9~17, 19~25, bs, 32H) 1.56 (CH-8, t, J=5.8, 1H) 3.30(CH₂-7, dd, J=1.8, 3.2, 2H) 3.67 (CH₂-6, m, 2H) 3.89 (CH-5, m, 1H) 4.87(CH-4, m, 1H)

TABLE 12 ¹³C-NMR δ (ppm) from TMS in CD₃OD 159.5589 (C-1) — (C-3) —(C-2) 76.7661 (C-4) 70.5853 (C-6) 70.3373 (C-5) 63.3933 (C-7) 39.9386(C-8) 33.0805 (C-16) 33.0805 (C-24) 31.9359 (C-9) 31.9073 (C-19) 31.1061(C-10) 31.0775 (C-11) 30.7627 (C-12) 30.6864 (C-13) 30.6864 (C-14)30.4765 (C-15) 30.4765 (C-22) 27.8153 (C-23) 27.7963 (C-20) 27.7295(C-21) 23.7329 (C-17) 23.7329 (C-25) 14.4521 (C-18) 14.4521 (C-26)

EXAMPLE 5

[Production Example 5 of Ascorbic Acid Derivative]

A sodium salt of 2-(2-heptylundecyl)-L-ascorbyl phosphate was producedas follows.

With nitrogen substitution, 249.5 grams (1.0 mole) of5,6-O-isopropylidene-L-ascorbic acid was added to 2000 ml of toluene,202.4 grams of triethylamine was dripped at room temperature, and themixture was stirred for one hour. Then, the mixture was cooled to −10degrees C., and 1003.9 grams (0.9 moles) of a toluene solution of(2-heptylundecyl)dichlorophosphate was dripped for one hour, and themixture was stirred at the temperature in the previous step for 14hours. To the thus obtained reaction mass, 12312 grams of an aqueoussolution of 6.7% hydrochloric acid was added, the mixture was hydrolyzedat 35 degrees C. for four hours, and the toluene layer was washed twicewith 1000 grams of an aqueous solution of 10% hydrochloric acid and 7.1%sodium chloride, and further washed once with an aqueous solution of 20%sodium chloride.

Then, an aqueous solution of 30% NaOH was added to the toluene layerthereof to adjust the pH value to 7. Ethanol was then added to theseparated aqueous layer thereof, the mixture thereof was subjected tovacuum concentration to remove water and ethanol by distillation, andthe thus deposited crystal was filtered and dried to obtain 344.9 gramsof a sodium salt of 2-(2-heptylundecyl)-L-ascorbyl phosphate (92.3% inpurity). The yield was 60.0% (based on L-ascorbic acid).

The molecular structure of the thus obtained compound was identified byinfrared absorption spectrum (IR) and nuclear magnetic resonancespectrum (¹H-NMR, ¹³C-NMR). It was confirmed that the thus obtainedcompound was an ascorbic acid derivative having the desired molecularstructure, i.e. a sodium salt of 2-(2-heptylundecyl)-L-ascorbylphosphate. Identification based on the results of peak positions and thecorresponding groups and carbon atoms were made in the same manner as inExample 1, so that its detailed description is omitted.

EXAMPLE 6

[Production Example 6 of Ascorbic Acid Derivative]

As will be apparent from the production steps shown by reaction formulasin FIG. 2, 2-heptylundecanol, which is a branched alkanol, was reactedwith phosphorus oxychloride to synthesize(2-heptylundecyl)dichlorophosphate, which is a monoalkyldichlorophosphate. The thus synthesized substance was reacted with5,6-O-isopropylidene-L-ascorbic acid obtained by reacting L-ascorbicacid with acetone, and the thus produced isostearyl-2-O-isopropylideneascorbyl phosphate was hydrolyzed with hydrochloric acid, washed,isolated and purified to produce 2-(2-heptylundecyl)-L-ascorbylphosphate. (In FIG. 2, the assigned numbers of peaks at ¹³C-NMR, whichis described later, are indicated.) Now the individual synthesis stepsare described in detail.

(1) Synthesis of 5,6-O-isopropylidene-L-ascorbic acid

With nitrogen substitution, 557.8 grams (9.6 moles) of acetone wascooled to −5 degrees C., 54.3 grams (0.2 moles) of 28% fuming sulfuricacid was dripped, and 176.1 grams (1.0 mole) of L-ascorbic acid wasadded. The mixture was then reacted at the temperature of the previousstep for 17 hours, filtered and washed with cold acetone to obtain 249.5grams of 5,6-O-isopropylidene-L-ascorbic acid (86.7% in purity) in theform of a wet cake.

(2) Synthesis of (2-heptylundecyl)dichlorophosphate

With nitrogen substitution, 540 ml of toluene and 138.0 grams (0.9moles) of phosphorus oxychloride were added and cooled to −10 degrees C.To this mixture, a solution of 243.5 grams (0.9 moles; 1.0 in molarratio) of 2-heptylundecanol and 91.1 grams (0.9 moles) of triethylaminewas dripped, and the mixture was reacted for 12 hours at 0 degrees C.The mixture was then heated to 25 degrees C., and a triethylaminehydrochloride was removed by filtering to obtain 1003.9 grams of atoluene solution of (2-heptylundecyl)dichlorophosphate (34.7% inconcentration).

(3) Synthesis of 2-(2-heptylundecyl)-L-ascorbyl phosphate

With nitrogen substitution, 249.5 grams (1.0 mole) of5,6-O-isopropylidene-L-ascorbic acid was added to 2000 ml of toluene,202.4 grams of triethylamine was dripped at room temperature, and themixture was stirred for one hour. Then, the mixture was cooled to −10degrees C., and 1003.9 grams (0.9 moles) of a toluene solution of(2-heptylundecyl)dichlorophosphate was dripped for one hour, and themixture was stirred at the temperature in the previous step for 14hours. To the thus obtained reaction mass, 12312 grams of an aqueoussolution of 6.7% hydrochloric acid was added, the mixture was hydrolyzedat 35 degrees C. for four hours, and the toluene layer was washed twicewith 1000 grams of an aqueous solution of 10% hydrochloric acid and 7.1%sodium chloride, and further washed once with an aqueous solution of 20%sodium chloride. The toluene layer was then subjected to columnchromatography, and a separated fraction thereof was subjected to vacuumconcentration (35 degrees C.; 2 Torr) to remove toluene by distillationto obtain 338.9 grams of 2-(2-heptylundecyl)-L-ascorbyl phosphate (94.6%in purity). The yield was 66.6% (based on L-ascorbic acid).

The molecular structure of the thus obtained2-(2-heptylundecyl)-L-ascorbyl phosphate was identified by infraredabsorption spectrum (IR) and nuclear magnetic resonance spectrum(¹H-NMR, ¹³C-NMR). It was confirmed that the thus obtained compound wasan ascorbic acid derivative having the molecular structure of formula[12], i.e. 2-(2-heptylundecyl)-L-ascorbyl phosphate.

EXAMPLE 7

[Production Example 7 of Ascorbic Acid Derivative]

Except that 2-heptylundecanol as used in Example 6 was used in the molarratio of 2.0 based on phosphorus oxychloride, a compound was produced inexactly the same manner as in Example 1. The compound obtained wasidentified by infrared absorption spectrum (IR) and nuclear magneticresonance spectrum (¹H-NMR, ¹³C-NMR). From these results (groups orcarbon atoms corresponding to the peak positions), it was confirmed thatthe thus obtained compound was an ascorbic acid derivative having thedesired molecular structure, i.e. 2-bis(2-heptylundecyl)-L-ascorbylphosphate (91.1% in purity). The yield was 20.1% (based on L-ascorbicacid).

EXAMPLE 8

[Production Example 8 of Ascorbic Acid Derivative]

A sodium salt of2-[2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]-L-ascorbylphosphate was produced as follows.

With nitrogen substitution, 249.5 grams (1.0 mole) of5,6-O-isopropylidene-L-ascorbic acid was added to 2000 ml of toluene,202.4 grams of triethylamine was dripped at room temperature, and themixture was stirred for one hour. Then, the mixture was cooled to −10degrees C., and 1003.9 grams (0.9 moles) of a toluene solution of[2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]dichlorophosphatewas dripped for one hour, and the mixture was stirred at the temperaturein the previous step for 14 hours. To the thus obtained reaction mass,12312 grams of an aqueous solution of 6.7% hydrochloric acid was added,the mixture was hydrolyzed at 35 degrees C. for four hours, and thetoluene layer was washed twice with 1000 grams of an aqueous solution of10% hydrochloric acid and 7.1% sodium chloride, and further washed oncewith an aqueous solution of 20% sodium chloride.

Then, an aqueous solution of 30% NaOH was added to the toluene layerthereof to adjust the pH value to 7. Ethanol was then added to theseparated aqueous layer thereof, the mixture thereof was subjected tovacuum concentration to remove water and ethanol by distillation, andthe thus deposited crystal was filtered and dried to obtain 344.9 gramsof a sodium salt of2-[2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]-L-ascorbylphosphate (92.3% in purity). The yield was 60.0% (based on L-ascorbicacid).

The molecular structure of the thus obtained compound was identified byinfrared absorption spectrum (IR) and nuclear magnetic resonancespectrum (¹H-NMR, ¹³C-NMR). It was confirmed that the thus obtainedcompound was an ascorbic acid derivative having the desired molecularstructure, i.e. a sodium salt of2-[2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl]-L-ascorbylphosphate.

Using the ascorbic acid derivatives obtained in Production Examples 1, 3and 4 as active ingredients, the cosmetic materials (lotions) ofExamples 8 to 12 were prepared. The contents of components forming eachascorbic acid derivative are shown in Table 13.

TABLE 13 Comparative Example of the invention Example 8 9 10 11 12 1 22-[2-(1,3,3-trimethyl- 0.05 0.5 5.0 — — 0.01 — n-butyl)-5,7,7-trimethyl-n-octyl]-L-ascorbyl phosphate 2-(2-hexyldecyl)-L- — — 10.0 — — —ascorbyl phosphate 2-bis(2-octyldodecyl)-L- — — — 10.0 — — ascorbylphosphate L-ascorbyl-2- — — — — — 2.0 glucoside sodium hydroxide — 0.20.2 0.05 ethanol 5.0 5.0 5.0 5.0 5.0 5.0 5.0 glycerin 10.0 10.0 10.010.0 10.0 10.0 10.0 POE hydrogenated 0.5 0.5 0.5 0.5 0.5 0.5 0.5 castoroil purified water balance balance balance balance balance balancebalance[Determination of the Skin-Whitening Effect]

For three months, every night and morning, each cosmetic material wasused by every member of one of a plurality of groups of subjects (eachgroup consisting of 20 subjects) who are suffering from spots, frecklesor darkened skin. At the end of the three-month period, the individualsubjects made evaluations for the effects of the cosmetic materials theyused by selecting one of the following four categories.

-   Markedly effective: Pigmentation is barely recognizable.-   Effective: Pigmentation has improved.-   Slightly effective: Pigmentation has slightly improved.-   Ineffective: No improvement in pigmentation has been observed.

Table 14 shows the results of evaluations, in which symbol ⊚ means thatnot less than 80% of the subjects evaluated the cosmetic material theyused as markedly effective or effective;

-   symbol ◯ means that not less than 60% and less than 80% of the    subjects evaluated the cosmetic material they used as markedly    effective or effective;-   symbol Δ means that not less than 40% and less than 60% of the    subjects evaluated the cosmetic material they used as markedly    effective or effective; and-   symbol X means that less than 40% of the subjects evaluated the    cosmetic material they used as markedly effective or effective.

TABLE 14 Comparative Example of the invention Example 8 9 10 11 12 1 2Skin-whitening effect after Δ ◯ ⊚ ⊚ ⊚ X Δ continuously applying cosmeticmaterial

As will be apparent from Table 14, at least 40% of the subjects who usedany of Examples 8 to 12, which contains a predetermined amount (not lessthan 0.05 percent by weight) of L-ascorbic acid-2-phosphate ester, feltthat they were markedly effective or effective. Also, more than 60% andmore than 80% of the subjects who used Examples 9 and Examples 10 to 12,respectively, evaluated the respective cosmetic materials as markedlyeffective or effective. Thus, it was confirmed that the skin-whiteningcosmetic material according to the present invention exhibitsphysiological activities that are inherent to L-ascorbic acid andbeneficial in whitening the skin.

The following are the composition of typical cosmetic materialscontaining L-ascorbic acid-2-phosphate ester as their active ingredient.The numerical values on the right column are the contents (percent byweight) of the respective components.

EXAMPLE 13 Gel Cream

2-(2-heptylundecyl)-L-ascorbyl phosphate 5.0 glycerin 10.0 ethanol 5.0sodium hydroxide 0.5 carboxyvinyl polymer 0.8 perfume adequate quantitypreservative adequate quantity purified water balance

EXAMPLE 14 Emulsion

2-(2-hexyldecyl)-L-ascorbyl phosphate 10.0 1,3-butylene glycol 10.0carboxyvinyl polymer 0.3 squalane 5.0 cetanol 0.8 L-arginine 0.3 perfumeadequate quantity preservative adequate quantity purified water balance

EXAMPLE 15 Cream

2-bis(2-octyldodecyl)-L-ascorbyl phosphate 10.0 1,3-butylene glycol 10.0carboxyvinyl polymer 0.3 squalane 5.0 cetanol 2.0 beeswax 3.0 L-arginine0.3 perfume adequate quantity preservative adequate quantity purifiedwater balance

1. An ascorbic acid derivative comprising an L-ascorbic acid-2-phosphateester or a salt thereof, wherein the phosphate ester has a branchedalkyl group which is branched at position 2, wherein the L-ascorbicacid-2-phosphate ester is represented by formula [1],

wherein R is a hydrogen (H) atom or an alkyl group branched at position2 and including 4 to 30 carbon atoms, but both R groups are not hydrogen(H) atoms, and wherein said branched alkyl group is 2-heptylundecylgroup, 2-octyldecyl group, 2-octyldodecyl group, 2-hexyldecyl group,2-hexyldodecyl group, 2-isoheptylisoundecyl group or2-(1,3,3-trimethyl-n-butyl)-5,7,7-trimethyl-n-octyl group.
 2. Theascorbic acid derivative of claim 1, comprising a salt selected from thegroup consisting of a sodium salt, a potassium salt, a magnesium saltand a calcium salt of the L-ascorbic acid-2-phosphate ester.
 3. Aprocess for producing the ascorbic acid derivative of claim 1, saidprocess comprising reacting a branched alkanol represented by formula[2],R—OH  [2] wherein R is an alkyl group branched at position 2 andincluding 4 to 30 carbon atoms, with phosphorus oxychloride tosynthesize monoalkyldichiorophosphate represented by formula [3],

wherein R is an alkyl group branched at position 2 and including 4 to 30carbon atoms, or dialkylmonochlorophosphate represented by formula [4],

wherein R is an alkyl group branched at position 2 and including 4 to 30carbon atoms, reacting the thus obtained substance with5,6-O-isopropylidene-L-ascorbic acid obtained by reacting L-ascorbicacid with acetone, and subjecting the thus obtained substance to acidhydrolysis.
 4. A process for producing the ascorbic acid derivative ofclaim 2, said process comprising reacting a branched alkanol representedby formula [2],R—OH  [2] wherein R is an alkyl group branched at position 2 andincluding 4 to 30 carbon atoms, with phosphorus oxychloride tosynthesize monoalkyldichlorophosphate represented by formula [3],

wherein R is an alkyl group branched at position 2 and including 4 to 30carbon atoms, reacting the thus obtained substance with5,6-O-isopropylidene-L-ascorbic acid obtained by reacting L-ascorbicacid with acetone, and subjecting the thus obtained substance to acidhydrolysis.